With the light-weighting and thinning development of smart cell phones and tablet computers, the touch display panel OGS (One Glass Solution) technology arises accordingly. The so-called OGS technology refers to a technology in which touch sensing electrodes (sensors) are produced directly onto a protective glass so as to reduce 1-2 layers of glass. This technology can achieve the effect of reducing the total thickness and the weight of a touch display panel, and it therefore has been highly developed in recent years.
At present, two techniques are mainly used in the preparation of OGS capacitive touch panels. One is a 6-step mask (6 mask) bridging technique, and the other is 5-step mask metal (5 mask metal) bridging technique. The 6-step mask (6 mask) bridging technique comprises the steps of:
1. preparing a black frame (i.e., a black matrix frame) by exposure and development;
2. preparing a pattern of touch sensing electrodes, wherein the touch sensing electrodes are conducted via an electrode chain along Y direction and are not conducted via an electrode chain along X direction;
3. preparing a transparent insulating layer, which covers the bridging positions of the electrode chain along Y direction;
4. depositing a layer of a touch sensing electrode material again on the insulating layer to allow the electrode chain along X direction to be conducted;
5. preparing metal wirings on the black frame, wherein electrode chains in X/Y directions are connected to a driving chip via the edge metal wirings; and
6. preparing an insulating layer after step 5 is finished, to protect the exposed metal wirings from being oxidized.
The 5-step mask metal (5 mask metal) bridging technique comprises the steps of:
1. preparing a black frame by exposure and development;
2. preparing a pattern of touch sensing electrodes, wherein the touch sensing electrodes are conducted via an electrode chain along Y direction and are not conducted via an electrode chain along X direction;
3. preparing a transparent insulating layer, which covers the bridging positions of the electrode chain along Y direction;
4. after the step 3 is finished, preparing metal bridges along X direction to allow the metal bridges to be connected, while preparing metal wirings on the black frame, wherein electrode chains in X/Y directions are connected to a driving chip via the edge metal wirings; and
5. after step 4 is finished, preparing an insulating layer to protect the exposed metal wirings from being oxidized.
Because the bridging points formed (i.e., the bridging points formed by the spatial crossing of the driving electrode chain and the sensing electrode chain) are invisible, the 6-step mask bridging technique has better effects and is mainly used in premium products. However, the 6-step mask bridging technique has relatively high costs, greatly limiting its general application in the OGS technology. The 5-step mask metal bridging technique reduces the number of masking processes in the production of a touch sensing electrode, that is, the process flow is shortened and the costs are saved. However, because metal bridging points are used in bridging positions formed by the spatial crossing of the driving electrode chain and the sensing electrode chain, there is a color difference at the bridging points and the visual effect is influenced, and this technique is typically used in low- and medium-grade products.